feat(backend): add BetterAuth email/password authentication

- Add PostgreSQL connection (src/db.ts)
- Configure BetterAuth with email/password (src/auth/index.ts)
- Add session middleware for route protection (src/auth/session-middleware.ts)
- Add registerAuthHandlers for mounting auth routes (src/auth/http.ts)
- Rename index.ts to server.ts
- Add .env.example with required environment variables

Co-authored-by: Ona <no-reply@ona.com>

apps/aris-backend/package.json

@@ -2,10 +2,10 @@
 	"name": "@aris/backend",
 	"version": "0.0.0",
 	"type": "module",
-	"main": "src/index.ts",
+	"main": "src/server.ts",
 	"scripts": {
-		"dev": "bun run --watch src/index.ts",
-		"start": "bun run src/index.ts",
+		"dev": "bun run --watch src/server.ts",
+		"start": "bun run src/server.ts",
 		"test": "bun test src/"
 	},
 	"dependencies": {
@@ -14,6 +14,9 @@
 		"@aris/source-weatherkit": "workspace:*",
 		"better-auth": "^1",
 		"hono": "^4",
-		"postgres": "^3"
+		"pg": "^8"
+	},
+	"devDependencies": {
+		"@types/pg": "^8"
 	}
 }